(Note: Literature references on the following background information and on conventional test methods and laboratory procedures well known to the ordinary person skilled in the art, and other such state-of-the-art techniques as used herein, are indicated in parentheses and appended at the end of the specification.)
Oxidative damage of proteins, lipids and nucleic acids has been implicated in diseases ranging from atherosclerosis to ischemia-reperfusion injury to cancer (1-3,16,32). Many lines of evidence also suggest that such damage plays a causal role in aging (1-3,23,28,33,34)). One important target may be proteins (3,33)), which play fundamental roles as biological catalysts, gene regulators and structural components of cells. One widely studied model of protein oxidation involves metal-catalyzed reactions that generate hydroxyl radical and other reactive species. These oxidants generate reactive carbonyls from certain amino acid residues (3,23,33). The discovery of elevated levels of protein carbonyls in many pathological states (3) and in tissues of old animals ((3,28,33,34) has implicated protein oxidation in the pa thogenesis of disease and aging.
A major difficulty in evaluating the roles of oxidants in human disease has been the lack of precise measures of oxidative stress in vivo (7). Many of the currently available methods are nonspecific and prone to artifacts. A powerful approach to studying the effects of oxidative pathways in vivo is the analysis of normal and diseased tissue for specific markers (9,18,26,30,31). Such markers have been identified as stable products of protein oxidation through in vitro studies.
The analysis of normal and diseased tissue, however, is inconvenient and unsatisfactory from various standpoints in view of its invasiveness to the patient's body and the need to manipulate and study the collected tissue and cellular matter in vitro. Accordingly, a noninvasive method for the determination of oxidative stress in vivo would have significant practical utility for determining oxidative stress in the patient and for subsequent therapeutic treatment of the patient.